The present invention relates to a method for the transmission of multimedia messages according to the preamble of the appended claim 1, a communication system according to the preamble of the appended claim 11, a multimedia terminal according to the preamble of the appended claim 18, as well as a communication system according to the preamble of the appended claim 19.
By means of a multimedia messaging service MMS, the user of a wireless communication device, such as a wireless terminal, can transmit multimedia messages to a receiving wireless communication device or terminal connected to the Internet data network. Such a multimedia message may contain various information, such as text, images, video information, sound, etc. When the user of a wireless communication terminal prepares a multimedia message for transmission, the user selects the target address as well as the content of the message. For transmitting e.g. a text-based e-mail message, an e-mail application is started in the wireless communication device, to give the receiver's e-mail address, to write the message in text format, and possibly to select one or more attachment files to be transmitted. After giving the transmit command, the program starts the transmission of the message by setting up a connection to a message switching centre or the like arranged in the mobile communication network. For this purpose, the number of this message service centre is advantageously stored in advance in the wireless communication device, wherein the user does not need to give this number separately for each e-mail transmission. After setting up of the connection, the e-mail is transmitted in a way known as such to the messaging centre, in which the connection data of the receiver of the message are examined. After this, the messaging centre tries to transmit the message to the receiver on the basis of these connection data.
In systems of prior art, the connection data of the receiver must be given in a certain format which depends on the type of the message transmission system. For example, when short messages are transmitted in the GSM mobile communication system, the receiver's connection data given is the receiver's mobile telephone number MSISDN (Mobile Station integrated International Service Digital Network), for example +358 40 123 4567. Correspondingly, in the Internet data network the address is typically in the format firstname.lastname@department.firm.com. This Internet address is transmitted in the Internet data network to a so-called domain name server DNS, which finds out the numerical address data of the domain on the basis of the domain part (department.firm.com) of this IP address. After this, the message is transmitted to this domain address, in which the domain server or the like finds out the correct target address within the domain, in this example by using the firstname.lastname part in front of the @ character, which is known as such.
The term “wireless communication system” refers generally to any communication system which enables a wireless data transmission connection between a wireless communication device (MS, Mobile Station) and the stationary parts in the system when the user of the wireless communication device moves within the service area of the system. A typical wireless communication system is a public land mobile network PLMN, such as the Global System for Mobile telecommunications GSM.
The term “Internet” is used generally to describe an information resource from which data can be retrieved with a data processing device, such as a personal computer (PC). The data processing device is in a data transmission connection via a modem to a telecommunication network. This information resource is distributed world-wide, cornprising several storage locations which are also in a data transmission connection to the telecommunication network. The Internet is made functional by defining certain data traffic standards and protocols, such as TCP (Transfer Control Protocol), UDP (User Datagram Protocol), IP (Internet Protocol), and RTP (Real time Transport Protocol), which are used to control data transmission between the large number of parts in the Internet data network. The TCP and UDP are involved in preventing and correcting data transmission errors in information to be transmitted in the Internet network, the IP processes the structure and routing of information, and the RTP is designed for real-time data transmission in the Internet data network. The Internet protocol versions presently in use are IPv4 and IPv6.
By using a wireless communication device, it is also possible to set up a connection to the Internet data network e.g. in such a way that a computer is connected to the wireless communication device which is thus used as a radio modem. The way of coupling to the mobile cornmunication network is thus a so-called circuit-switched connection. For such a circuit-switched connection, resources are allocated all the time, irrespective of whether there is anything to transmit.
The general packet radio service GPRS is a new service under development in the GSM mobile communication system. The appended FIG. 1 shows connections of a telecommunication network in a packetswitched GPRS service. The main element in the network infrastructure is a GPRS support node, so-called GSN. It is a mobility router for implementing the coupling and cooperation between different data networks, e.g. to a public switched packet data network PSPDN via a connection Gi or to the GPRS network of another operation via a connection Gp, mobility management with GPRS registers via a connection Gr, and the transmission of data packets to wireless communication devices MS irrespective of their location. Physically, the GPRS support node GSN can be integrated in a mobile switching centre MSC, or it can be a separate network element based on the architecture of the data network routers. User data is passed directly between the support node GSN and the base station subsystem BSS consisting of base transceiver stations BTS and base station controllers BSC, but there is a signalling connection Gs between the support node GSM and the mobile services switching centre MSC. In FIG. 1, continuous lines between blocks illustrate data transmission (i.e. the transmission of speech and/or data in digital format), and broken lines illustrate signalling.
Physically, the data can be transmitted transparently via the mobile switching centre MSC.
The radio interface between the wireless communication device MS and the landline network is conveyed via the base transceiver station BTS and is indicated with the reference Um. The references Abis and A, respectively, describe the interface between the base transceiver station BTS and the base station controller BSC and between the base station controller BSC and the mobile switching centre MSC, which is a signalling connection. The reference Gn describes a connection between different support nodes of the same operator. The support nodes are normally divided into gateway support nodes GGSN (Gateway GSN) and serving support nodes SGSN (Serving GSN), as shown in FIG. 1.
Consequently, the GPRS service makes it possible to transmit packetformat information between a wireless communication device and an external data network, wherein certain parts of the mobile communication network constitute an access network.
The operation of the wireless communication device MS and the support node SGSN can be divided into different layers, each of them having a different purpose, as shown in FIG. 2. Information to be transmitted between the wireless communication device MS and the support node SGSN, for example control signalling and information transmitted by the user, is transmitted preferably in the form of data frames. The data frame of each layer consists of a header field and a data field.
The information contained in a data field can be e.g. information entered by the user of a wireless communication device, or signalling data. The following is a description of the functional tasks of the layers in the GPRS system.
In the data link layer, the lowermost layer is the MAC layer (Media Access Control) which takes care of the use of the radio channel in traffic between the wireless communication device MS and the base station subsystem BSS, such as the allocation of channels for the transmission and reception of packets.
At the lowermost level, data transmission between the base station subsystem BSS and the support node SGSN takes place in the L2 layer (data link layer) using a link layer protocol, such as the LAPD protocol, the frame relay protocol, or the like. The L2 layer may also contain quality or routing data according to the GPRS specifications.
The L2 layer has properties of the physical layer and the data link layer according to the OSI model.
Above the MAC layer, there is the RLC layer (Radio Link Control), which serves the purpose of dividing the data frames generated by the LLC layer into packets of a determined length to be transmitted on the radio channel (PDU, Protocol Data Unit), transmitting the packets, and retransmitting, if necessary. In the GPRS system, the length of the packets is the length of one GSM time slot (ca. 0.577 ms).
The LLC layer (Logical Link Control) offers a reliable communication link between the wireless communication device MS and the support node SGSN. For example, the LLC layer supplements the message to be transmitted with error correction data, whereby it is possible to try to correct incorrectly received messages and retransmit the message, if necessary. Furthermore, data encryption and decryption takes place in the LLC layer.
In the SNDCP layer (Sub-Network Dependent Convergence Protocol), protocol changes, compressing and segmenting of information to be transmitted, as well as the segmenting of messages coming from an upper layer, take place. An SNDCP frame advantageously comprises an SNDCP header and an SNDCP data field. The SNDCP header consists of protocol data (Network Service Access Point Identity, NSAPI) and SNDCP control data, such as compressing, segmenting and encryption specifications. The SNDCP layer is used as a protocol adapter between protocols used at an upper layer (IP/X.25) and the protocol of the LLC layer (data link layer).
The information to be transmitted preferably comes from an application to the SNDCP layer in the form of data packets according to a protocol (PDP, Packet Data Protocol), such as in messages according to the X.25 protocol or in packets according to the Internet protocol (IP). The application can be e.g. a data application of the wireless communication device, a telecopy application, a computer program in a data transmission connection with the wireless communication device, etc.
The SNDCP frame is transferred to the LLC layer, in which the frame is supplemented with an LLC header. The LLC header comprises e.g. an LLC control element which defines the frame number and command type (info, acknowledgement, retransmission request, etc.). In connection with accessing the GPRS packet network, the wireless communication device transmits a log-in request message to the support node SGSN. On the basis of the device identification of the wireless communication device (IMSI, International Mobile Station Identity), the support node SGSN can retrieve information from the home register HLR corresponding to the wireless communication device in question, wherein the support node SGSN can, using this information, select a temporary logical link identity (TLLI) for the data transmission connection.
If the wireless communication device has previously had a TLLI identity in its use, the wireless communication device transmits it in the request message, wherein the support node SGSN can give this identity to the use of the wireless communication device again, or reserve a new TLLI identity. The support node SGSN transmits the TLLR identity of its selection to the wireless communication device, to be used in the data transmission connection between the wireless communication device and the support node SGSN. This TLLI identity is used in the communication to determine, which data transmission connection each message belongs to. The same TLLI identity must not be used in more than one data transmission connection at the same time. After the end of the connection, the TLLI identity used in the connection can be given to a new connection to be set up.
Cells in a packet network are divided into routing areas in such a way that each routing area comprises several cells. Thus, the mobility management functions of the wireless communication device are used to maintain information about the location and connection state of wireless communication devices in the service area of the packet network. This information is maintained both in the wireless communication device and in the packet network, preferably in the GPRS support node SGSN.
To use GPRS services, the wireless communication device first performs a log-in in the network (GPRS attach), whereby the wireless communication network reports that it is ready for packet data transmission.
The GPRS attach sets up a logical link between the wireless communication device and the support node SGSN, enabling the transmission of short messages (SMS, Short Message Services) via the GPRS network, paging services via the support node, and informing about incoming packet data to the wireless communication device.
In connection with the GPRS attach of the wireless communication device, the support node also sets up a mobility management (MM) function and performs user identification. To transmit and receive information, the packet data protocol (PDP) is activated, whereby the wireless communication device is allocated a packet data address to be used in the packet data connection, wherein the address of the wireless communication device is known in the gateway support node.
Consequently, at the GPRS attach, a data transmission connection is set up to the wireless communication device, to the support node and to the gateway support node, the connection being allocated a protocol (for example X.25 or IP), a connection address (e.g. an X.121 address), the quality of service, and the network service access point identifier (NSAPI). The wireless communication device activates the packet data connection with an activate PDP context request, in which the wireless communication device reports the temporary logical link identity (TLLI), the type of the packet data connection, the address, the requested quality of service, the network service access point identifier, and possibly also the access point name (APN).
The GSM system is a time division multiple access (TDMA) system, in which traffic on the radio channel is time-divided, taking place in successively repeated TDMA frames, each of which consisting of several (eight) time slots. In each time slot, a data packet is transmitted in a radio-frequency burst having a finite duration and consisting of a sequence of modulated bits. The time slots are primarily used as control channels and traffic channels. The traffic channels are used for the transmission of speech and data, and the control channels are used for signalling between the base transceiver station BTS and wireless communication devices MS1.
With an increase in the multimedia properties of wireless communication devices and mobile communication networks, there are more frequently situations in which multimedia messages should be transmitted from a wireless communication device to very different types of target addresses, for example to another wireless communication device or to a multimedia terminal connected to the Internet data network. Thus, in methods and systems of prior art, the problem occurs, how the address data of these different types of target addresses can be transmitted to the message switching centre. Particularly in such transmission, in which the same message is intended to be transmitted to several receivers with different types of terminals, according to prior art the message must be transmitted either separately to different types of receiver addresses or the message switching centre must store information about the address type and address for each receiver. In this latter case, the updating of information causes extra work, and on the other hand the receiver may have several alternatives for receiving multimedia messages, wherein all the different alternatives should be stored in the message switching centre.
The transmission of multimedia messages can be implemented in such a way that the address data is always given in a certain format, e.g. as an MSISDN address or an SMTP address. If only an MSISDN address is in use, messages cannot be transmitted from a wireless terminal to the receiver's terminal connected to the Internet network. However, if only an SMTP address is in use, the message switching centre cannot check whether the wireless terminal of the receiver is connected to the mobile communication network, because information in the home register of the mobile communication network cannot be retrieved in systems of prior art, if only the SMTP address of the receiving terminal is known.